Polyacetal polymers, which are commonly referred to as polyoxymethylenes, have become established as exceptionally useful engineering materials in a variety of applications. Polyoxymethylene polymers, for instance, are widely used in constructing molded parts, such as parts for use in the automotive industry and the electrical industry. Polyoxymethylene polymers, for instance, have excellent mechanical properties, fatigue resistance, abrasion resistance, chemical resistance, and moldability.
Although polyacetal resins possess many useful properties, the polymers have a tendency to degrade when heated and are inherently unstable in an oxidative atmosphere or in an acidic or alkaline environment. In particular, polyacetal resins have a tendency to emit formaldehyde during processing and after the polymer has been molded into a part. Formaldehyde is not only a contaminant, but can also adversely affect metallic components that may be placed in association with the polymer. For example, formaldehyde readily oxidizes to formic acid which can corrode metals or cause discoloration.
In view of the above, those skilled in the art have attempted to combine polyacetal polymers with various compounds in order to lower formaldehyde emissions. For instance, in the past, polyacetal polymers have been combined with melamines in order to achieve lower formaldehyde emission performance. In addition, various other chemical compounds have been suggested for lowering formaldehyde emissions.
Although various chemical compounds used in the past have successfully lowered formaldehyde emissions from products made from polyoxymethylene polymers, further improvements in formaldehyde emissions are needed. For instance, stricter government regulations continue to require further Improvements in reducing formaldehyde emissions.
Unfortunately, however, when additives are combined with a polyacetal polymer in order to enhance one property, the additive may have an adverse impact on another property. For example, adding greater amounts of formaldehyde scavengers into polyoxymethylene polymer compositions can compromise one or more properties of the polymer. For instance, excess amounts of formaldehyde scavengers may increase the occurrence of mold deposits and/or begin to adversely affect other physical properties.
In view of the above, a need exists for an improved formaldehyde stabilizer package capable of further reducing formaldehyde emissions without adversely affecting other properties of the polyoxymethylene polymer composition.